Krosis means both sorry and sorrow. The phrase the draugr use it in means "eternal sorrow." It wouldn't make sense for them to apologise considering the in-game book Amongst the Draugr proves they were servants of the Dragon Cult in life and thus aren't protecting their tombs/Dragon Priests against their will.

Ha i dont think hagravens are scary in the slightest, playing skyrim in the dark with surround sound can make me jump though. D:

Well, Draugr have never scared me, they have pissed me off, but never scared, not that I'm not scared by scary things, but draugr are just a bit too generic zombie, and they attack you with weapons instead of munching on you, so they're at least hygienic zombies

However, if Draugr scare this guy, just imagine what will happen to him when he goes to that Hagraven infested cave during the Companions quests! xD